A conventional image forming apparatus such as a digital MFP (multi-functional peripheral) adjusts a position of an image using a predetermined image pattern. However, since a precise size of a sheet actually used is not necessarily constant even if it is a fixed size sheet, it may be necessary to perform an image adjustment again. The precise size of the sheet may vary depending on manufacturer of sheets even if the sheets are indicated as the same size, and may also vary depending on humidity or the like. For this reason, it is difficult for the image forming apparatus to carry out image adjustment suitable for sheets that are to be actually used, during a manufacturing process. The sheet used by the image forming apparatus for printing may shrink due to heat applied to the sheet in a fixing processing or the like. Therefore, in such an image forming apparatus, it may be difficult to carry out the image adjustment in consideration of a change in the size of the sheet due to the fixing processing.